Conventional arc welders utilize different methods to weld thin metal sheets having thickness smaller than 2 mm, and these usually comprise laser welders which are capable of welding super-thin metal sheets. However, these welding machines are very costly and therefore have a very limited market. Another known technology for welding thin metal sheets is the ion welders, and these are also very expensive and costly to maintain. Another type of known welding machine for welding thin metal sheets is the gas isolation welder. It is a bulky machine and pollutes the environment as they burn propane gas and are not suitable for welding thin sheets. They are also very dangerous to handle due to the risk of explosion of the gas, and require excessive maintenance.
The major problem that one encounters when welding thin metal sheets is to try and control the arc initiation and welding arc such as not to overheat or burn through the metal sheet. Puncturing occurs in metal sheets due to the high temperature created by the high voltage and current necessary to initiate the arc, and this often occurs in the area where the electrode has to touch the thin metal part in order to cause an arc to form. A large surge of voltage and current must be produced in order to generate an initial arc. To generate an arc the welder must pull back the welding electrode a short distance above the metal sheet very quickly. Thereafter, the welding arc must be maintained at a substantially reduced current flow in order not to cause the sheet to heat up, which can cause puncture or melt through. Because of the problem in welding thin metal sheets, conventional arc welding machines of the prior art are not used when the sheets are below 4 mm in thickness.
Welding circuits have been designed in the prior art in an attempt to solve the above-mentioned problem. However, known welding circuits do not provide the necessary automatic control and fine adjustment which is required when welding very thin or super-thin metal sheets or metal parts together. With known circuit designs considerable trial and error attempts are made in welding the thin metal parts, and this results in substantial waste of expensive material, low productivity, low product yield rate, loss of expensive time, and low quality products. These welding machines also require highly skilled labor, expensive machinery, and are usually time consuming to set up. Also, when the thin metal is punctured or melted through the molten metal debits usually scatter over other parts, and additional labor is required to clean up the scattered metal and to repair the punctured holes in the metal pieces. Accordingly, no adequate solution has been developed for welding thin or super-thin metal parts, such as metal pieces having thicknesses in the range of about 0.2 to 2.0 mm.